Two or more persons living in same household who are related by blood, marriage, or adoption. (No families are recognized in group quarters. ) All persons living in a household related to each other are regarded as one family. For instance, a son of the head and his wife living in the household are treated as part of the heads family.

The number of families does not necessarily equal the number of households, since not all households include families. Families are classified in the complete-count basic records by family size or number of persons in a family from 2 persons to 35 persons. Average number of persons per family is calculated.

Married couple with or without own children, or one parent with one or more own children (parent-child group), living in a housing unit and related to the household head, but excluding the head (for example, a son, his wife and children, living with the household head). Since subfamily members are counted as part of the heads (primary) family, too, the number of subfamilies is not included in the count of families per seer in any tabulations for families. Census basic records include categories of sub-families by family type.

In 1960, a family in a household whose head was not related to the household head. In 1970, secondary families are not recognized (since there are so few); persons formerly classed as secondary family members are classed as secondary individuals.

Ascertained for all persons 14 years of age and over for the preceding calendar year, even if they had no income. Total income is the sum of the dollar amounts of money respondents reported receiving (best estimate if exact amount not known) as wages or salary income, net nonfarm and farm self-employment income, and other income, as specified below. In statistics on family income or household income, the combined incomes of all members of each family or household are treated as a single amount. For unrelated individual income and for income statistics of persons 14 years and over, the classification is by the amount of their own (individual) total income.

Income is tabulated by several intervals. For example, under $1,000, $1,000- $1,999... $9,000-$9,999, $10,000-$14,999, $15,000- $24,999, $25,000 and over. The 1960 census basic records included dollar amounts for each type of income in intervals of $10 from $1-$9 to $9,990-$9,999 and in intervals of $1,000 from $10,000-$10,999 to $24,000-$24,999. Two separate categories were provided for each of the following items: (1) no income and (2) incomes of $25,000 and over. (Net loss from self-employment and all other sources was included in intervals of $100 from $1 - $99 to $9,800-$9,899. Net losses of $9,900 and over were tabulated separately.)

In the 1970 census basic records, for dollar amounts of each type of income, questionnaire dollar entries within $100 intervals from $1-$99, $100-$199, to $99,900- !$99,999 are shown as one-tenth of the midpoint value for that interval. For example, any questionnaire entry between $100 and $199 is represented as 15 on the basic record; any questionnaire entry between $99,900 and $99,999 is represented as 9995 on the basic record. Similarly, dollar amounts within $10,000 intervals from $100,000-$109,999, $110,000-$119,999 to $980,000-$989,999 are shown as one-tenth of the midpoint value for that interval. For example, any questionnaire entry between $100,000 and $109,999 is represented as 10500 on the basic record; any questionnaire entry between $980,000 and $989,999 is represented as 98500 on the basic record. Separate categories are provided for no income and incomes of $990,000 or more. Net losses from self-employment income (section 104.12 below) and income from all other sources (section 104.23 below) are included in intervals of $100 from $1-$99 to $9,800-$9,899. Net losses of $9,900 or more are carried as one category.

Median and mean incomes are calculated for families, unrelated individuals, and persons 14 years and over for total income and for each type of income. (In the 1960 derivation of aggregate amounts for calculating mean income, persons in the open-ended interval $25,000 and over were assigned an estimated mean of $50,000 for each income type. In the 1970 derivation of aggregate amounts for each income type, persons in the open-ended interval $990,000 and over are assigned an estimated mean of $995,000.)

Money respondents reported receiving as wages, salary, commissions, bonuses, or tips from all jobs (before deductions for taxes, bonds, dues, etc.). Respondents were to include sick leave pay, but exclude military bonuses, reimbursements for business expenses, and pay in kind.

Money respondents reported receiving as profits or fees (net income after business expenses) from their own business, professional practice, partnership, or farm. (If the enterprise lost money, respondents were to report the amount of loss. ) In 1970, self-employment income from a farm (including earnings as a tenant farmer or sharecropper, excluding payment in kind) was reported separately from other self-employment income.

Money respondents reported receiving from sources other than wages or salary and self-employment. In 1960, respondents were asked to report other income as a single amount. In 1970, respondents were asked to specify other income as follows.

Includes amounts received from Federal, State, and local public programs such as aid for dependent children, old-age assistance, general assistance, and aid to the blind or totally disabled. Excludes separate payments for hospital or other medical care.

In the 1960 census, selected tabulations were prepared for the Puerto Rican population in areas outside the five Southwestern States where Spanish surname population was identified.

In the 1970 census, the Spanish-American population is defined differently according to the sample a person is enumerated in and his State of residence. All tabulations except those for 5-percent data are based upon a 15-percent sample, defined as follows:

b. In the five southwestern States (Arizona, California, Colorado, New Mexico, and Texas), persons of Spanish language (see 67.1 below) or persons not of Spanish language but of Spanish surname identified by matching with a list of about 8,000 such names.

Tabulations of 5-percent data are for persons who report Spanish origin or descent including Mexican, Puerto Rican, Cuban, Central or South American, and other Spanish. Spanish origin or decent is ascertained by means of a 5-percent sample question new with the 1970 census.